arXiv subjects

Anil Kumar

Publications and source records attributed to Anil Kumar.

At least 73 records · Page 4Linked to original sources

arXiv2023

Chirality-Induced Magnetization of Magnetite by an RNA Precursor

Life is homochiral and homochirality is a fundamental feature of living systems on Earth. While the exact mechanism that led to homochirality is still not fully understood, any realistic scenario on the origins of life needs to address the emergence of homochirality. In order to impose and maintain chirality in a prebiotic network, an environmental factor functioning as a chiral agent is demanded. Magnetized surfaces are prebiotically plausible chiral agents, shown to be effective in enantioseparation of ribose-aminooxazoline (RAO), a ribonucleic acid (RNA) precursor, due to the chiral-induced spin selectivity (CISS) effect. As such, mechanisms for breaking the magnetic symmetry of magnetic minerals are of the utmost importance. Here we report the avalanche magnetization of magnetite $(Fe_{3}O_{4})$ by the crystallization of enantiopure RAO. The observed breaking of the magnetic symmetry is induced by the chiral molecules due to the CISS effect and spreads out across the magnetic surface like an avalanche, providing a way to uniformly magnetize a magnetic surface without fully covering it. Considered together with our previous results on enantioseparation by crystallization on a magnetic surface, chirality-induced avalanche magnetization paves the way for a cooperative feedback between chiral molecules and magnetic surfaces. With this feedback, a weak natural bias in the net magnetization can be amplified and spin-selective processes can be accommodated on magnetic minerals on a persistent basis.

physics.chem-ph↗

arXiv2023

Trust in Shared Automated Vehicles: Study on Two Mobility Platforms

The ever-increasing adoption of shared transportation modalities across the United States has the potential to fundamentally change the preferences and usage of different mobilities. It also raises several challenges with respect to the design and development of automated mobilities that can enable a large population to take advantage of this emergent technology. One such challenge is the lack of understanding of how trust in one automated mobility may impact trust in another. Without this understanding, it is difficult for researchers to determine whether future mobility solutions will have acceptance within different population groups. This study focuses on identifying the differences in trust across different mobility and how trust evolves across their use for participants who preferred an aggressive driving style. A dual mobility simulator study was designed in which 48 participants experienced two different automated mobilities (car and sidewalk). The results found that participants showed increasing levels of trust when they transitioned from the car to the sidewalk mobility. In comparison, participants showed decreasing levels of trust when they transitioned from the sidewalk to the car mobility. The findings from the study help inform and identify how people can develop trust in future mobility platforms and could inform the design of interventions that may help improve the trust and acceptance of future mobility.

cs.HC↗

arXiv2023

Hybrid stars are compatible with recent astrophysical observations

Compact stars (CS) are stellar remnants of massive stars. Inside CSs the density is so high that matter is in subatomic form composed of nucleons. With increase of density of matter towards the centre of the objects other degrees of freedom like hyperons, heavier non-strange baryons, meson condensates may appear. Not only that at higher densities, the nucleons may get decomposed into quarks and form deconfined strange quark matter (SQM). If it is so then CSs may contain SQM in the core surrounded by nucleonic matter forming hybrid stars (HSs). However, the nature and composition of matter inside CSs can only be inferred from the astrophysical observations of these CSs. Recent astrophysical observations in terms of CS mass-radius (M-R) relation and gravitational wave (GW) observation indicate that the matter should be soft in the intermediate density range and stiff enough at higher density range to attain the maximum possible mass above $2~M_\odot$ which is not compatible with pure hadronic equation of states (EOSs). Consequently, we study the HS properties with different models of SQM and find that within vector bag model considering density dependent bag parameter, the model goes well with the astrophysical observations so far.

astro-ph.HE↗

arXiv2022

Forbidden beta decay properties of $^{135,137}$Te using shell-model

In this work, the large-scale shell-model calculations for $β$-decay properties have been done. The $β$-delayed $γ$-ray spectroscopy has been performed recently at ILL, Grenoble [M. Si \textit{et al.}, Phys. Rev. C {\bf 106}, 014302 (2022)] to study $β$-decay properties corresponding to $^{137}$Te (($7/2^-))$ $\rightarrow$ $^{137}$I ($J_f$) transitions. We have done a systematic shell-model study for nuclear structure properties and compared the obtained results with the experimental data. Finally, the $β$-decay properties such as the $\log ft$ values and average shape factors have been reported. This is the first theoretical calculation for the $\log ft$ values corresponding to these new experimental data. In addition, we have also reported calculated $\log ft$ results for $^{135}$Te (($7/2^-))$ $\rightarrow$ $^{135}$I ($J_f$) transitions.

nucl-th↗

arXiv2022

Fragile electronic superconductivity in Bi Single crystal

It was presumed that semimetal Bismuth (Bi) would not show superconductivity (SC) even at ultra-low temperatures ($<$10 mK) due to its very low carrier density ($\approx 3\times10^{17}$cm$^{-3}$). Recently, we have established bulk superconductivity in ultra-pure (99.9999\%) Bi single crystal at $\mathrm{T_C = 0.53}$ mK with an extrapolated upper critical field $\mathrm{H_C(0) = 5.2μ}$T measured along the [$0001$] (trigonal) -crystallographic direction. At very low concentrations of the charge carriers, we are dealing with fragile Cooper pairs with an estimated large coherence length $\mathrm{ξ_{GL}(0)\approx 96 μ}$m. We also stated that one needs to go beyond the conventional electron-phonon coupling (BCS-like) mechanism to understand the SC state in Bi. Bi is a compensated semi-metal with electrons and holes as charge carriers. In order to find the charge carriers responsible for the SC, we report the temperature dependence of the anisotropic critical field along the [$01\bar 10$] (bisectrix)-crystallographic direction and compared it with the earlier data from measurements along the trigonal. Our theoretical analysis of the anisotropy of critical fields suggests that the light electrons in the three pockets of Bi bands are responsible for the SC and indicates that Bi is an extremely weak type-II (close to type-I) superconductor. Finally, we review the current theories proposed to explain the SC in Bi.

cond-mat.supr-con↗

arXiv2022

Shell-model description for the properties of the forbidden $β^-$ decay in the region "north-east" of $^{208}$Pb

In the present work, we report a comprehensive shell-model study of the $\log ft$ values for the forbidden $β^-$ decay transitions in the north-east region of $^{208}$Pb. For this we have considered $^{210-215}$Pb $\rightarrow$ $^{210-215}$Bi and $^{210-215}$Bi $\rightarrow$ $^{210-215}$Po transitions. We have performed shell-model calculation using KHPE interaction in valence shell 82-126 for protons and 126-184 for neutrons without any truncation. We have also calculated half-lives and Q-values for the concerned nuclei. Recently several $\log ft$ values are observed corresponding to $β^-$ decay from (8$^-$) isomeric state of $^{214}$Bi$^m$ at CERN-ISOLDE facility [Phys. Rev. C {\bf 104}, 054301 (2021)], and for the first time we have reported shell-model results for these transitions.

nucl-th↗

arXiv2022

Probing Lorentz Invariance Violation with Atmospheric Neutrinos at INO-ICAL

The possibility of Lorentz Invariance Violation (LIV) may appear in unified theories, such as string theory, which allow the existence of a new space-time structure at the Planck scale ($M_p \sim 10^{19}$ GeV). This effect can be observed at low energies with a strength of $\sim 1/M_p$ using the perturbative approach. In the minimal Standard Model extension (SME) framework, the neutrino mass-induced flavor oscillation gets modified in the presence of LIV. The Iron Calorimeter (ICAL) detector at the proposed India-based Neutrino Observatory (INO) offers a unique window to probe these LIV parameters by observing atmospheric neutrinos and antineutrinos separately over a wide range of baselines in the multi-GeV energy range. In this paper, for the first time, we study in detail how the CPT-violating LIV parameters $(a_{μτ}, a_{eμ}, a_{eτ})$ can alter muon survival probabilities and expected $μ^-$ and $μ^+$ event rates at ICAL. Using 500 kt$\cdot$yr exposure of ICAL, we place stringent bounds on these CPT-violating LIV parameters at 95\% C.L., which are slightly better than the present Super-Kamiokande limits. We demonstrate the advantage of incorporating hadron energy information and charge identification capability at ICAL while constraining these LIV parameters. Further, the impact of the marginalization over the oscillation parameters and choice of true values of $\sin^2θ_{23}$ on LIV constraints is described. We also study the impact of these LIV parameters on mass ordering determination and precision measurement of atmospheric oscillation parameters.

hep-ph↗

arXiv2022

Emergence of an island of extreme nuclear isomerism at high excitation near $^{208}$Pb

Metastable states with T$_{1/2}$ = 8(2) ms in $^{205}$Bi and T$_{1/2}$ = 0.22(2) ms in $^{204}$Pb, with $\approx $ 8 MeV excitation energy and angular momentum $\ge $ 22 $\hbar $, have been established. These represent, by up to two orders of magnitude, the longest-lived nuclear states above an excitation energy of 7 MeV, ever identified in the nuclear chart. Additionally, the half-life of the 10.17 MeV state in $^{206}$Bi has been determined to be 0.027(2) ms, the next highest value in this highly excited regime. These observations indicate the emergence of an island of extreme nuclear isomerism arising from core-excited configurations at high excitation in the vicinity of the doubly closed-shell nucleus $^{208}$Pb. These results are expected to provide discriminating tests of the effective interactions used in current large-scale shell-model calculations.

nucl-ex↗

arXiv2022

Compact star merger events with stars composed of interacting strange quark matter

We investigate the properties of stars participating in double compact star merger events considering interacting model of stable strange quark matter. We model the matter making it compatible with the recent astrophysical observations of compact star mass-radius and gravitational wave events. In this context we consider modified MIT bag model and vector bag model with and without self interaction. We find new upper bound on tidal deformability of $1.4~M_\odot$ strange star corresponding to the upper bound of effective tidal deformability inferred from gravitational wave event. Range of compactness of $1.4~M_\odot$ strange star is obtained as ${0.175}\leq{C_{1.4}}\leq{0.199}$. Radius range of $1.5M_\odot$ primary star is deduced to be ${10.57}\leq{R_{1.5}}\leq{12.04}$ km, following stringent GW170817 constraints. GW190425 constraints provide with upper limit on radius of $1.7$ solar mass strange star that it should be less than $13.41$ $\text{km}$.

astro-ph.HE↗

arXiv2022

Lithography Free Process for the Fabrication of Periodic Silicon Micro/Nano-Wire Arrays and Its Light-trapping Properties

Vertically aligned silicon micro/nanowire arrays of different sizes have been synthesized by combining the modified metal-assisted chemical etching (MACE) and reactive ion etching (RIE) methods. This is a novel lithography-free method to fabricate silicon micro/nanowire arrays. The size of micro/nanowire arrays is controlled by controlling the etching rate and diameter of silica particles. The silicon micro/nanowire geometry can utilize for efficient collection of photo-generated charge carriers from impure silicon wafers, which have a short minority carrier diffusion length also act as a self-antireflection coating layer. For micro/nanowire having average diameters of 40 nm, 330 nm and 950 nm and their corresponding average length 1.12 micron, 1.1 micron, and 1 micron, respectively, the observed average reflectance was 0.22, 0.6 and 0.33 percent at 45-degree incident angle, while the average reflectance was increased up to 4.2, 9.2, and 11 percent, respectively at 75-degree incident angle in the broad range of 300 - 1200 nm of the solar spectrum. The measured average reflectance for these samples is quite low compared to the planar silicon wafer. Thus this geometry is a promising candidate for fabricating low-cost and highly efficient radial junction silicon micro/nanowire arrays based solar cells.

cond-mat.mtrl-sci↗

arXiv2022

Lithography free method to synthesize the ultra-low reflection inverted-pyramid arrays for ultra-thin silicon solar cell

Silicon inverted pyramids arrays have been suggested as one of the most promising structure for high-efficient ultrathin solar cells due to their ability of superior light absorption and low enhancement of surface area. However, the existing techniques for such fabrication are either expensive or not able to create appropriate structure. Here, we present a lithography free method for the fabrication of inverted pyramid arrays by using a modified metal assisted chemical etching (MACE) method. The size and inter-inverted pyramids spacing can also be controlled through this method. We used an isotropic chemical etching technique for this process to control the angle of etching, which leads to ultra-low reflection, even < 0.5%, of this nanostructure. Using this specification, we have predicted the expected solar cell parameters, which exceeds the Lambertian limit. This report provides a new pathway to improve the efficiency of the ultrathin silicon solar cells at lower cost.

cond-mat.mtrl-sci↗

arXiv2022

Confinement Highlights the Different Electrical Transport Mechanisms Prevailing in Conducting Polymers

We study the differences in electrical charge transport dynamics of the conductivity enhancement of poly(3,4-ethylenedioxythiophene) (PEDOT) derivatives under geometrical confinement. The results of polymer blend poly(3,4-ethylene dioxythiophene):poly(styrenesulfonate) and a polymer-monomer blend, poly(3,4- ethylenedioxythiophene):tosylate, highlight the role of dopants and processing conditions of these systems under confinement. The prevailing transport length scales in confined geometry of characteristic dimensions originate from varying disorder in these polymer systems. These observable differences in two different PEDOTs introduced by molecular level reorganization can be utilized to tune conducting polymer systems for efficient electrical and thermoelectric properties. The electrical conductivity σ of the polymer system, which is a function of the electronic structure at molecular level and a connectivity parameter, has been probed in cylindrical-alumina nanoscaffolds of various channel diameters, at different frequencies ω and temperatures T. The observations also emphasize the role of disorder in these conducting polymer systems.

cond-mat.mtrl-sci↗

arXiv2021

Shell-model study for GT-strengths corresponding to $β$ decay of $^{60}$Ge and $^{62}$Ge

In the present work, we have reported a comprehensive shell-model study of GT-strengths for recently available experimental data for $^{60}$Ga and $^{62}$Ga from RIKEN Nishina Center [Phys. Rev. C 103, 014324 (2021)] populated by $β$ decay of the $^{60}$Ge and $^{62}$Ge, respectively. We have performed shell-model calculations in two different model spaces, the first set of calculations in the $fp$ model space using KB3G and GXPF1A interactions, while the second set in $f_{5/2}pg_{9/2}$ model space using JUN45 and jj44b effective interactions. Our shell-model results in $fp$ model space are in a reasonable agreement with the available experimental data.

nucl-th↗

arXiv2021

Probing the Earth's Core using Atmospheric Neutrinos at INO

The proposed 50 kt Iron Calorimeter (ICAL) detector at the India-based Neutrino Observatory (INO) aims to detect atmospheric muon neutrinos and antineutrinos separately in the multi-GeV range of energies and over a wide range of path lengths. While passing through the Earth, the upward-going neutrinos experience a density-dependent matter effect, which can be utilized to extract information about the internal structure of Earth. Since the Earth's matter effect modifies the neutrino oscillation patterns differently for neutrinos and antineutrinos, the capability of ICAL to distinguish $μ^-$ and $μ^+$ events plays an important role in observing this matter effect. Taking advantage of good angular resolution, ICAL would be able to observe about 331 $μ^-$ and 146 $μ^+$ events corresponding to the core-passing neutrinos and antineutrinos, respectively, in 10 years. We demonstrate for the first time that ICAL would be able to validate the presence of Earth's core by ruling out a two-layered profile consisting of only mantle and crust in fit with respect to the PREM profile in data with a median $Δχ^2$ of 7.45 for normal mass ordering (NO) and 4.83 for inverted mass ordering (IO) using 500 kt$\cdot$yr exposure. If we do not use the charge identification capability of ICAL, these sensitivities deteriorate to a $Δχ^2$ of 3.76 for NO and 1.59 for IO.

hep-ph↗

arXiv2021

Baryonic dense matter in view of gravitational-wave observations

The detection of gravitational waves from the merger of binary neutron stars events (GW170817, GW190425) and subsequent estimations of tidal deformability play a key role in constraining the behaviour of dense matter. In addition, massive neutron star candidates ($\sim 2 M_{\odot}$) along with NICER mass-radius measurements also, set sturdy constraints on the dense matter equation of state. Strict bounds from gravitational waves and massive neutron stars observations constrain the theoretical models of nuclear matter comportment at large density regimes. On the other hand, model parameters providing the highly dense matter response are bounded by nuclear saturation properties. This work analyses coupling parametrizations from two classes based on covariant density functional models: Non-Linear and Density-Dependent schemes. Considering these constraints together, we study possible models and parametrization schemes with the feasibility of exotic degrees of freedom in dense matter which go well with the astrophysical observations as well as the terrestrial laboratory experiments. We show that most parametrizations with non-linear schemes do not support the observations and experiments while density-dependent scheme goes well with both. Astrophysical observations are well explained if the inclusion of heavier non-strange baryons is considered as one fraction of the dense matter particle spectrum.

astro-ph.HE↗

arXiv2021

Validating the Earth's Core using Atmospheric Neutrinos with ICAL at INO

The Iron Calorimeter (ICAL) detector at the proposed India-based Neutrino Observatory (INO) aims to detect atmospheric neutrinos and antineutrinos separately in the multi-GeV range of energies and over a wide range of baselines. By utilizing its charge identification capability, ICAL can efficiently distinguish $μ^-$ and $μ^+$ events. Atmospheric neutrinos passing long distances through Earth can be detected at ICAL with good resolution in energy and direction, which enables ICAL to see the density-dependent matter oscillations experienced by upward-going neutrinos in the multi-GeV range of energies. In this work, we explore the possibility of utilizing neutrino oscillations in the presence of matter to extract information about the internal structure of Earth complementary to seismic studies. Using good directional resolution, ICAL would be able to observe 331 $μ^-$ and 146 $μ^+$ core-passing events with 500 kt$\cdot$yr exposure. With this exposure, we show for the first time that the presence of Earth's core can be independently confirmed at ICAL with a median $Δχ^2$ of 7.45 (4.83) assuming normal (inverted) mass ordering by ruling out the simple two-layered mantle-crust profile in theory while generating the prospective data with the PREM profile. We observe that in the absence of charge identification capability of ICAL, this sensitivity deteriorates significantly to 3.76 (1.59) for normal (inverted) mass ordering.

hep-ph↗

arXiv2021

Second-forbidden nonunique $β^-$ decays of $^{59,60}$Fe: Possible candidates for $g_A$ sensitive electron spectral-shape measurements

In this work, we present a theoretical study of the electron spectral shapes for the second-forbidden nonunique $β^-$-decay transitions $^{59}\textrm{Fe}(3/2^-)\to\,^{59}\textrm{Co}(7/2^-)$ and $^{60}\textrm{Fe}(0^+)\to\,^{60}\textrm{Co}(2^+)$ in the framework of the nuclear shell model. We have computed the involved wave functions by carrying out a complete $0\hbarω$ calculation in the full $fp$ model space using the KB3G and GXPF1A effective interactions. When compared with the available data, these interactions predict the low-energy spectra and electromagnetic properties of the involved nuclei quite successfully. This success paves the way for the computations of the $β$-decay properties, and comparison with the available data. We have computed the electron spectral shapes of the mentioned decay transitions as functions of the value of the weak axial coupling $g_{\rm A}$. By comparing these computed shapes with the measured spectral shapes allows then to extract the effective value of $g_{\rm A}$ for these decay transitions. This procedure, coined the spectrum-shape method (SSM) in several earlier studies, complements the method of determining the value of $g_{\rm A}$ by reproducing the (partial) half-lives of decay transitions. Here we have enhanced the original SSM by constraining the value of the relativistic vector matrix element, $^V\mathcal{M}^{(0)}_{KK-11}$, using the conserved vector-current hypothesis (CVC) as a starting point. We hope that this finding would be a strong incentive to measure the spectral shapes in the future.

nucl-th↗

arXiv2021

Shell-model description for the first-forbidden $β^-$ decay of $^{207}$Hg into the one-proton-hole nucleus $^{207}$Tl

In this work, we have performed large-scale shell-model calculations for the first-forbidden $β^{-}$ decay of $^{207}$Hg into the one-proton-hole nucleus $^{207}$Tl corresponding to the recently available experimental data from ISOLDE-CERN [T. A. Berry et al., Phys. Rev. C 101, 054311 (2020)]. We have used the one-particle one-hole ($1p$-$1h$) truncation for both protons and neutrons simultaneously across the doubly-shell closure at $^{208}$Pb in the final states of $^{207}$Tl. In our calculations, we have also considered the effect of mesonic enhancement $ε_{\mathrm{mec}}=2.01\pm 0.05$ in the rank-0 for the axial-charge matrix element $γ_{5}$. Here, we have calculated the $\log ft$ values from the ground-state of $^{207}$Hg to the several excited states of $^{207}$Tl and obtained a good agreement between the calculated and the experimental data. In the experimental data spin and parity for some states are not yet confirmed, thus based on the shell-model results for the $\log ft$ values we have given the prediction for these states. This is the first theoretical calculation for the $\log ft$ values for these transitions.

nucl-th↗